The demand for gasoline as a motor fuel is one of the major factors which dictates the design and mode of operation of a modern petroleum refinery. The gasoline product from a refinery is derived from several sources within the refinery including, for example, gasoline from the catalytic cracking unit, straight run gasoline, gasoline obtained as a low boiling by-product from various refinery operations, especially catalytic processes such as catalytic dewaxing, and reformate. The octane number of the gasoline from these different sources varies according to the nature of the processing and the octane rating of the final gasoline pool will depend upon the octane ratings of the individual components in the pool as well as the proportions of these components. The increasing use of unleaded gasoline coupled with increasing engine efficiencies in road vehicles has led to a demand for increased gasoline pool octane which, in turn, makes it desirable to increase the octane values of the individual components of the pool. Although there are various ways of achieving this objective, some necessarily involve compromises which may render them less attractive in commercial refinery operation. For example, the octane rating of straight-run naphtha may be improved by reforming over a noble metal/acid catalyst, which converts aliphatic and cycloaliphatic hydrocarbons to higher octane aromatics. However, such treatment can entail a significant yield loss resulting from deleterious side reactions such as cracking and coking. Alternative measures for increasing pool octane are therefore still desirable.
Another trend which is perceptible in the petroleum refining industry is towards the reduction of benzene and other aromatics in the gasoline pool. In the United States, the Clean Air Act specifies various motor fuel content standards and similar measures are being considered in the European Community. Benzene is particularly prevalent in reformer gasoline, being a distinctive product of the reforming process, produced by the dehydrogenation of C.sub.6 cycloparaffins, the dehydrocyclization of straight chain paraffins of appropriate chain length (C.sub.6) and dealkylation of other aromatics. Accordingly, it would be desirable to provide an alternative to reforming of naphtha which would provide the desired increase in octane without increasing aromatics content or decreasing yield. It would also be desirable to treat a reformate prepared under low severity conditions which avoid severe yield losses, by enhancing its octane values without increasing aromatics content.
Aromatic amines possess higher blending octane values than their hydrocarbon analogues so that they are desirable components for the refinery gasoline pool. Amination of aromatic components present in a gasoline boiling range feedstock therefore represents an attractive means for providing a significant improvement in the octane rating of the gasoline pool without increasing its aromatics content. Preparation of aromatic amines by reducing nitro compounds is known in the art. The reduction of nitro compounds with hydrogen can be carried out in vapor or liquid phase over a variety of hydrogenation catalysts. Further information on these hydrogenation processes is found in Kirk-Othmer, Encyclopedia of Chemical Technology, Third Ed., Vol. 2 at pp. 355-376, in an article entitled "Amines by Reduction."